1. Field of the Invention
This invention relates to a process for preparing a liquid fuel composition which comprises liquefying coal, separating a mixture of phenols from said liquefied coal, converting said phenols to the corresponding mixture of anisoles, subjecting at least a portion of the remainder of said liquefied coal to hydrotreatment, subjecting at least a portion of said hydrotreated liquefied coal to reforming to obtain reformate and then combining at least a portion of said anisoles and at least a portion of said reformate to obtain said liquid fuel composition.
2. Description of the Prior Art
Coal liquids obtained by the hydrogenation of coal promise to be a significant source for hydrocarbons suitable for use in generating energy, for example, as liquid hydrocarbon fuel compositions for spark ignition internal combustion engines. Such coal liquids contain a significant amount of phenolic materials, ranging, for example, from about five to about 30 weight percent, based on the raw coal liquids so produced. If coal liquefaction becomes commercially significant, far more phenolic compounds will probably be produced than can be absorbed by the combined demands of all chemical industries utilizing phenolic materials. It would be highly desirable, therefore, to find other non-chemical industry users for such phenolic materials. It is known, for example, that anisole can be added to gasoline as a non-metallic octane improver. However, phenols in gasoline can be corrosive, can cause gum formation and can cause some plastics and elastomers now in use in automotive gasoline systems to swell, harden and/or crack. Just as important, phenols are poisonous by all routes of entry into the systematic circulation of mammals, absorption through the skin being the primary route of entry into the blood stream. Liquid phenols in contact with the skil can also cause local irritation or chemical burns.
On the other hand, the phenols need not be removed from the raw coal liquid. Instead the total coal liquid product, after removing ash and heavy bottom material therefrom, could be further processed to high quality gasoline blending stock or distillate fuel. Hydrotreatment would, for example, reduce the phenolics of fuel-compatible hydrocarbons. Unfortunately, such hydrotreatment to reduce phenolics to such fuel-compatible hydrocarbons would require severe treating conditions and would consume large amounts of hydrogen.
From a processing point of view refining of coal liquids is greatly hampered by the presence of phenols for the following reasons. As pointed out above, excessive hydrogen consumption is required to reduce the phenols. Phenols are corrosive to processing equipment. The combination of phenols and chlorides, when present, are more corrosive to processing equipment than either one alone. Most coals contain chlorides, thus usually aggravating the corrosion problems. Water produced when phenols are hydroreduced will tend to sinter refinery catalyst supports. The presence of phenols during hydrotreating tends to hamper the ease of nitrogen removal from the coal liquids. For example, the rate constants for removal of nitrogen from phenolfree coal liquids by hydrotreatment can be increased by a factor of six at 375.degree. to 400.degree. C. compared to the same coal liquids containing the phenols. The significance of the increased hydrodenitrogenation rate constants is that the reactor can be smaller for a given capacity or more throughput can be obtained at milder conditions, both of which can result in lower operating costs.